1. Field of the Invention
The present invention relates to a high-Tc oxide superconductor of a Bi-Sr-Ca-Cu-O system and a method for producing the high-Tc oxide superconductor.
2. Description of the Background Art
In a conventional oxide superconductor of a Y-Ba-Cu-O system, its critical temperature Tc, at which the resistance becomes completely zero, is relatively high such as up to 90 K. However, in order to obtain high and good characteristics, it is necessary to set a composition ratio of Y:Ba:Cu to exactly 1:2:3, and it is quite difficult to control this composition ratio. Further, this superconductor is unstable and readily reacts with water or carbon dioxide to deteriorate its characteristics, and thus changes with the passage of time in the air. That is, this unstable superconductor must be handled carefully, e.g., it must be stored apart from the air.
An oxide superconductor of a Bi-Sr-Ca-Cu-O system having a relatively high critical temperature Tc has been proposed. However, in actual, it is difficult to determine its producing conditions, and the obtained superconductor is liable to separate into two phases. Its zero resistance temperature is 75 K. at most, and hence none of such superconductors operates in stable at temperature 77 K. of liquid nitrogen. Accordingly, the application fields of the conventional superconductors are largely restricted.